1. Field of the Invention
The invention relates to an electrostatic discharge protection circuit. More particularly, the invention relates to an electrostatic discharge protection circuit corresponding to a reset signal wiring.
2. Description of the Related Art
With the development of semiconductor technology, the integrated circuit imports some cutting-edged producing procedure. Therefore, the electronic product may have higher performance, smaller size, and lower power consumption. More and more circuit components are integrated into a compact system-on-chip (SoC) especially on some handheld electronic devices, e.g. mobile phone, digital camera, and personal digital assistant (PDA). Accordingly, the digital product with a tiny size may provide best performance.
In modern microelectronic circuits, the die size is shrinking with an exponential speed. Highly integrated electronic system nowadays is driven by some precise triggering signal, so as to perform some functions or judgment at a high frequency. However, the electronic system may be affected by the external or internal noise. For example, the electrostatic discharge (ESD) is one of the unstable factors in the microelectronic system. Unexpected ESD may cause malfunctions to some circuit components within the electronic system.
In general, there are two main effects of the ESD to the internal circuit. The first one is that a high discharging current may impact and damage the electron channel of the internal circuit during the electrostatic discharging. The other one is that the control signal wiring or input/output port of the IC may be interfered by the discharging current during the electrostatic discharging, and it may cause the system crash or malfunction.
In an integrated circuit chip, there are usually some important signal wirings, e.g. clock (CLK) wiring, enable (EN) wiring and reset (RST) wiring. For example, unexpected ESD may false-trigger the reset wiring in the chips, such that some working components or important references may be forced to reset accidentally. In this case, some function of the system may fail, or even the whole system may crash down. Sometimes, it needs to reboot the whole system or re-install firmware to repair the system. Therefore, the repair procedure may cost a lot of time and effort.
In order to prevent the ESD current from damaging the internal circuit, most electronic devices in prior art implement the ESD protection system. The ESD protection system is used for maintaining the reference voltage of the control signal wiring on a specific level, so as to prevent the false-triggering. However, the ESD protection system in prior art needs some specific circuit structure and firmware for operating and judging, so that the traditional ESD protection system is more complex. In other words, it needs both hardware and firmware working together for elevating the ESD protection capability.
The invention discloses an ESD protection circuit capable of detecting the electrostatic discharging, and it can maintain the level of the reset signal wiring when the electrostatic discharge is happening. In this way, the ESD protection circuit may avoid false-triggering on the reset signal wiring, so as to solve aforesaid problems.